Unraveling Cold Molecular Collisions: Stark Decelerators in Crossed-Beam Experiments

In the last two decades, enormous progress has been made in the manipulation of molecular beams. In particular, molecular decelerators have been developed with which advanced control over neutral molecules in a beam can be achieved. By using arrays of inhomogeneous and time‐varying electric (or magnetic) fields, bunches of molecules can be produced with a tunable velocity, narrow velocity spreads, and almost perfect quantum‐state purity. These monochromatic or “tamed” molecular beams are ideally suited to be used in crossed‐molecular‐beam scattering experiments. Here, we review the first generation of these “cold and controlled” scattering experiments that have been conducted in the last decade and discuss the prospects for this emerging field of research in the years to come. Crash course: Stark decelerators can be used in crossed‐beam scattering experiments (see picture) to study molecular collisions with the highest possible level of detail. Ten years ago, this combination of techniques was used for the first time. An overview of the experiments that have been performed to date by using this powerful combination of techniques is presented.